Shopsmith Forums

Well, after breaking free the main table bolts and aligning the table (separate post from last week), I used my Mark V a lot this past week. Everything worked fine up until today. I was trying to rip some maple for drawer runners and the motor starting speeding up and slowing down and then finally stopped altogether tripping the panel breaker. This happened a couple more times even when not cutting. The other thing I noticed was that the speed controller was not properly changing speeds when I would turn the speed controller down and then up. It would stay at a fairly high constant rpm. The motor housing was also getting hot. I turned the machine off and waited about a half hour and tried again. The motor would get up to a high rpm even though the speed controller was set at slow. After about fifteen seconds it would quit. This is really disappointing since I had the headstock overhauled this past Spring. Any ideas on what I can do to get it running properly again?

theinrichs wrote:Well, after breaking free the main table bolts and aligning the table (separate post from last week), I used my Mark V a lot this past week. Everything worked fine up until today. I was trying to rip some maple for drawer runners and the motor starting speeding up and slowing down and then finally stopped altogether tripping the panel breaker. This happened a couple more times even when not cutting. The other thing I noticed was that the speed controller was not properly changing speeds when I would turn the speed controller down and then up. It would stay at a fairly high constant rpm. The motor housing was also getting hot. I turned the machine off and waited about a half hour and tried again. The motor would get up to a high rpm even though the speed controller was set at slow. After about fifteen seconds it would quit. This is really disappointing since I had the headstock overhauled this past Spring. Any ideas on what I can do to get it running properly again?

Perhaps the floating sheave(motor shaft) is sticking in a closed position(belt riding close to the outer edge). Attempting to adjust the speed towards slow (closing the idler pulley) would create a condition where the belt would be 'too short' and the belt may get jammed...

Not clear is if the motor is changing speed, or if the quill shaft is changing speed, or both???

I would check the floating sheave for adequate lubrication and freedom of movement(open/close).

Thanks, Dusty! I’m a fellow Kentuckian although I’ve been in San Diego since 1990 courtesy of the U.S. Navy and retired from the Navy eight years later. My wife and I originally are from Newport, across the Ohio River from Cincinnati. I went to the University of Louisville and my wife went to UK!

To answer your question, the motor wasn’t changing speeds even though I was turning the speed controller. It seemed to be stuck at a constant high speed. I will try your suggestions. Should I try this repair with the headstock in drill press mode or by taking the headstock off the tubes? I was looking at Jacob’s you tube videos and he has one where he works on the sheaves.

You are welcome to any assistance I might be able to provide but I did now comment on your current problem. The thanks, I believe, should be for JPGs input.

It might be helpful to know where on the sheaves the belt is currently positioned. It seems clear that the sheaves are not changing position when you attempt to alter speed. Understand that the motor does not change speed. The desired speed change is achieved by changing the pulley ratios (the sheaves).

Of particular interest is where the belt rides on the upper (control) sheave. Is it close to the outer edge of the sheave or is it deep in the sheave?

Have you recently lubricated the sheaves?

Hopefully, the attached will clarify what I mean regarding belt position in the sheaves. The depiction on the right is at high speed. For every rotation of the motor the upper sheave will rotate 2.41 times (2.41 times faster than the motor). The depicted motor rotates at 3450rpm.

Note: This is a concept drawing and even though it details dimensions it is NOT intended to represent actual design parameters. The measurements were taken on one of my Mark Vs.

theinrichs, you have received advice from two of the premier members here. Rest assured your Mark V is a VERY reliable and tough tool. If it was "rebuilt" recently, then my add to this discussion is that your maint. methods/frequency need adjusting. If maintained correctly these mechanical speed change machines are bullet proof. Do what Dusty and JPG are suggesting, and then keep oiling the pertinent places regularly and the machine will be trouble free for decades.

Just my .02

theinrichs wrote:Thanks, Dusty! I’m a fellow Kentuckian although I’ve been in San Diego since 1990 courtesy of the U.S. Navy and retired from the Navy eight years later. My wife and I originally are from Newport, across the Ohio River from Cincinnati. I went to the University of Louisville and my wife went to UK!

To answer your question, the motor wasn’t changing speeds even though I was turning the speed controller. It seemed to be stuck at a constant high speed. I will try your suggestions. Should I try this repair with the headstock in drill press mode or by taking the headstock off the tubes? I was looking at Jacob’s you tube videos and he has one where he works on the sheaves.

Do not let that 'Wildcat' from Arizona confuse thee. That is a different breed of wildcat!

One thing concerns me greatly. It is necessary to be very explicit when describing this beast. My question was 'what' was changing speed. You stated "the motor wasn’t changing speeds even though I was turning the speed controller".

This indicates to me a misunderstanding of how the beast works.

First the MOTOR does not change speeds when the speed control dial is adjusted. The motor only alters speed as a result of mechanical loading etc..

Speed dial adjustments alter the position of a control sheave(the middle pulley in Dusty's diagram) along the idler shaft that causes the idler pulley to open/close(right pix/left pix).

The floating sheave on the motor pulley(the lower pulley) responds by moving thus closing/opening.

My suspicion is that the floating sheave may be stuck and does not allow the pulley to open up and thus reduce the speed of the other pulleys.

IF I understand your meaning, the quill shaft rpm remains fast even though the speed control dial is adjusted towards slow. To get ANY reduction in speed would require great torque to be applied to the speed control dial to even get it to move.

I fear we may be not be completely/accurately understanding what is actually occurring

One thing that may be confusing is the sound that is made at the different RPM's. If one didn't know better they would assume the noise change from high RPM to low RPM is the motor changing speeds, when it is the other innards of the machine that are making most of the noise. With no belts attached, it is quite surprising how quiet the motor actually is.

First of all, my apologies to JPG for my blunder in confusing him with Dusty, the other AZ Wildcat! From this mistake and the questions I ask I'm sure you can tell I'm a newbie to this forum.

Thank you all for your tips. JPG and Dusty are obviously quite correct in explaining that the Mark V motor doesn't change speeds when using the speed dial. From all of your explanations I now better understand the working relationships of the motor, speed dial and control and floating sheaves. I will try your suggestions and report back. Thanks, again.

This is good. This is what many of us are here for. All we want is to assist wherever assistance is needed and where we are capable.

Be safe as you continue on this learning exploratory. If something does not feel right, sound right, look right - hesitate to continue. Be safe.

Another 'possibility' is the control sheave is sticking OPEN and the belt is POSSIBLY dropping down and jamming between the sheaves.

And the control sheave bearing/clip/quadrant gear interface is not correct.

Again pictures are extremely helpful in our attempts to diagnose thy problem.